This invention relates generally to golf club heads of the so-called metal-wood type, and to methods of making such heads.
Golf club heads of the so-called metal-wood type are well known in the art for use in place of traditional wooden headed clubs such as drivers, 3-woods, and the like. Metal-wood clubs typically have a hollow club head formed from cast metal components, such as stainless steel or the like. A typical cast head is formed by separately casting a sole plate and a downwardly opening head shell, and then welding the sole plate onto the cast head shell. The geometry of the metal club head generally is selected to conform with that of the corresponding wooden headed club. The hollow interior of the head is often filled with foam or other material to reduce the "ping" noise resulting from impact with a ball.
Metal-wood club heads are relatively difficult and expensive to manufacture. Metal casting techniques inherently produce a variety of surface imperfections, such as pit holes or other blemishes, which are difficult and time consuming to remove. Excess grinding to remove such blemishes can adversely affect head weight distribution as well as structural integrity, and also results in variations in the head geometry from club to club. Because of this scrap rates as high as 30 percent are normal in the field, considerably increasing production costs. Even with these scrap rates, the standard error in loft angle of the striking face of a cast metal wood club head is typically of the order of .+-.1.degree., which can cause a significant difference in operation from club to club.
Another problem is that the casting process is inherently expensive and does not allow the head geometry to be varied without significant additional expense. In the golfing field, different individuals will have different requirements as regards such variables as loft angle, lie or inclination angle of the club shaft, as well as the amount the striking face is open or closed (i.e. the angle from toe to heel of the club). Lie angle is very important when fitting a golf club to a particular golfer. When the player is striking a golf ball, it is important that the sole of the club is seated perfectly with respect to the ground. Thus, a taller player would need to have a shaft with a greater lie angle (more upright) than a shorter person whose hands will be closer to the ground. The amount the face of the club is open or closed will also be very important to a golfer, depending on their experience level, and can be used to control any tendency to hook or slice the ball. Additionally, variation in the loft angle or vertical inclination of the face plate is desirable between stronger and weaker players. A weaker golfer requires more face loft angle to compensate for lack of club head velocity, whereas strong players typically prefer a club with less than average loft angle.
Each specific club head having a certain loft angle, shaft angle, and face angle from heel to toe, typically requires a unique set of relatively costly casting dies. Thus, several sets of casting dies are needed to provide even a relatively small range of different club head geometries which will not be ideal for every individual.